Semiconductor device

ABSTRACT

To improve resistance to instantaneous surge power of semiconductor devices having resistor films. The semiconductor device includes: a semiconductor substrate; a first insulating film formed on the semiconductor substrate; a polysilicon resistor film formed on the first insulating film; a second insulating film formed on the resistor film; a high heat conductor film consisting of a highly heat-conducting material formed on the second insulating film; and a pair of terminal wirings and formed on the second insulating film and connected to the resistor film, in which a thickness T 3  of the second insulating film is thinner than a thickness T 2  of the resistor film.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device, and moreparticularly to a semiconductor device that comprises a resistor filmconsisting of polysilicon formed in an insulating film on asemiconductor substrate.

[0003] 2. Background Art

[0004]FIG. 5 is a sectional view showing a schematic configuration of aconventional integrated circuit that comprises polysilicon resistors. Inthis drawing, reference numeral 1 is a silicon substrate, i.e. asemiconductor substrate; 2 is an insulating film consisting of a fieldoxide film or an interlayer insulating film formed on the siliconsubstrate 1, 3 is a resistor film consisting of polysilicon formed inthe insulating film 2; 4A and 4B are terminal wirings of the resistorfilm 3 formed on the insulating film 2, and connected to the resistorfilm 3 through connecting portions 5A and 5B.

[0005] The integrated circuit comprising a conventional resistor film isconstituted as described above, and heat generated in the resistor film3 is dissipated into the silicon substrate 1 through the insulating film2 underneath the resistor film 3, but the heat is not sufficientlytransferred because the insulating film 2 underneath the resistor film 3is as thick as about 0.5 μm, thereby raising a problem of low resistanceto instantaneous surge electric power.

[0006] Specifically, as shown by curve a in FIG. 3 that indicates theresult of simulation of the temperature rise of the resistor film 3 inthe case where a step electric power of about 3 mW was consumed, atemperature rise per unit power consumption was as large as 2,200deg./W, in 1 μs showing a large transient heat impedance.

[0007] Also, as shown by curve a in FIG. 4 that indicates the result ofESD (electrostatic discharge) simulation of discharge from a 200 pFcapacitor, temperature rose rapidly in 700 ns after starting powersupply to over 2,000 K, leading to thermal breakdown.

[0008] In recent years, since the resistor film 3 is becoming thinneraccompanying the size reduction of transistors due to the advancement ofmicro machining technology, the resistance to surge power tends tofurther lower.

SUMMARY OF THE INVENTION

[0009] Therefore, an object of the present invention is to cope withsuch a problem, and to provide a semiconductor device that can improve aresistance to a surge power of integrated circuits or the like havingresistor films.

[0010] According to one aspect of the present invention, a semiconductordevice comprises a semiconductor substrate, a first insulating filmformed on the semiconductor substrate, a polysilicon resistor filmformed on the first insulating film, a second insulating film formed onthe resistor film, a high heat conductor film consisting of a highlyheat-conducting material formed on the second insulating film, and apair of terminal wirings formed on the second insulating film andconnected to the resistor film, wherein a thickness of the secondinsulating film is thinner than a thickness of the resistor film.

[0011] According to another aspect of the present invention, asemiconductor device comprises a semiconductor substrate, a firstinsulating film formed on the semiconductor substrate, a polysiliconresistor film formed on the first insulating film, a second insulatingfilm formed on the resistor film, a high heat conductor film consistingof a highly heat-conducting material formed on the second insulatingfilm, and a pair of terminal wirings formed on the second insulatingfilm and connected to the resistor film, wherein a thickness of the highheat conductor film is thicker than a thickness of the resistor film.

[0012] According to the present invention, the resistance toinstantaneous surge power of the semiconductor devices having resistorfilms can be improved.

[0013] Other and further objects, features and advantages of theinvention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a sectional view showing a schematic constitution ofEmbodiment 1.

[0015]FIG. 2 is a top view showing a schematic constitution ofmodification of Embodiment 1.

[0016]FIG. 3 is a graph of characteristic curves showing the results ofa temperature rise simulation obtained to clarify the constitution ofEmbodiment 1 as well as to confirm the effect

[0017]FIG. 4 is a graph of characteristic curves showing the results ofan ESD simulation obtained to clarify the constitution of Embodiment 1as well as to confirm the effect

[0018]FIG. 5 is a sectional view showing a schematic configuration of aconventional integrated circuit that comprises polysilicon resistors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

[0019] Embodiment 1 of the present invention will be described belowreferring to the drawings.

[0020]FIG. 1 is a sectional view showing a schematic constitution ofEmbodiment 1. In FIG. 1, reference numeral 1 is a silicon substrate,i.e. a semiconductor substrate; 2 is an insulating film consisting of afield oxide film or an interlayer insulating film formed on the siliconsubstrate 1; 3 is a resistor film consisting of polysilicon formed inthe insulating film 2; 4A and 4B are terminal wirings of the resistorfilm 3 formed on the insulating film 2, and connected to the resistorfilm 3 through connecting portions 5A and 5B.

[0021] Reference numeral 6 denotes a high heat conductor film consistingof a high heat conductor material formed above the resistor film 3through a thin insulating film 2A, and is made of aluminum (Al) or analloy thereof.

[0022] T1 is a thickness of the insulating film 2 (silicon oxide film)provided underneath the resistor film 3, for example 0.5 μm. T2 is thethickness of the resistor film 3, for example 0.15 μm. T3 is a thicknessof the insulating film 2A (silicon oxide film) between the resistor film3 and the high heat conductor film 6. T4 is a thickness of the high heatconductor film 6. Specific values of T3 and T4 will be described later.

[0023] Embodiment 1 is constituted as described above. Thereby, since aheat path is produced from the resistor film 3 to the high heatconductor film 6 through the thin insulating film 2A over the resistorfilm 3, in addition to a path for dissipating heat into the siliconsubstrate 1 through the thin insulating film 2 underneath the resistorfilm 3, a heat capacity of the high heat conductor film 6 cantemporarily absorb the heat generated in the resistor film 3 due tosurge power until the heat is accumulated in the high heat conductorfilm 6, thus improving the resistance to the surge power.

[0024] In this case, since the pulse width of the surge current isusually about 0.2 μs, the heat generated in the resistor film 3 passesthrough the insulating film 2A in about the above-described time andreaches the high heat conductor film 6. Furthermore, in order tomaintain the heat absorption by the high heat conductor film 6thereafter, a thickness T3 of the insulating film 2A becomes animportant factor.

[0025] Similarly as an interlayer film used in general IC processes,when the thickness T3 of the insulating film 2A is, for example, 0.5 μm,the time for heat to pass is about 1 μs. Therefore, the thickness is toothick for a pulse width of the above-described surge current to expectsufficient effect.

[0026] Also, since the heat transferred to the high heat conductor film6 scarcely diffuses to a lateral direction because of the narrow pulsewidth of a surge current, a heat absorption must be supplemented byincrease in thickness.

[0027]FIGS. 3 and 4 are graphs of characteristic curves showing theresults of a temperature rise simulation and an ESD simulation obtainedto clarify the constitution of Embodiment 1 as well as to confirm theeffect, and show characteristics of each of T3 and T4 when thethicknesses of T3 and T4 is set to various values in the structure shownin FIG. 1, for example, T1=0.5 μm and T2=0.15 μm. That is, in thesecharacteristic diagrams, a curve b shows when T4=1 μm and T3=0.2 μm, acurve c shows when T4=0.2 μm and T3=0.1 μm, a curve d shows when T4=0.45μm and T3=0.1 μm, and a curve e shows when T4=1 μm and T3=0.1 μm.

[0028] As seen in the curves c, d, and e of FIG. 4, when the thicknessT3 of the insulating film 2A on an upper surface of the resistor film isT3=0.1 μm, thinner than the thickness T2=0.15 μm of the resistor film 3,a peak temperature lowers to 1,400 K, then the permanent breakdown doesnot occur. However, as seen in the curve b, when the thickness T3=0.2μm, thicker than the thickness of the resistor film 3, a temperaturerises rapidly causing permanent breakdown, and it is seen that aresistance to surge power is low.

[0029] For the thickness T4 of Al of the high heat conductor film 6,when T4=0.2 μm or more, thicker than the thickness of the resistor film3, permanent breakdown does not occur, as seen in any of curve c (T4=0.2μm), curve d (T4=0.45 μm), and curve e (T4=1 μm).

[0030] When the curves c, d, and e are compared, the peak temperature ofthe curve d or curve e where the thickness T4 of Al is twice thethickness T2 of the resistor film 3 or more, 0.45 μm or 1 μm,respectively, is nearly 200 K lower than a peak temperature of the curvec, achieving larger effect. Furthermore, when transient heat impedancecharacteristics in the above-described cases are viewed from FIG. 3, aninstantaneous temperature rise up to 0.4 μs is large in the curve b andthe curve a (prior art) in FIG. 4, which lead to permanent breakdown,and it is seen that characteristics up to this time point aresignificantly related to the occurrence of ESD breakdown.

[0031] From the above results, in Embodiment 1, it was concluded, toobtain the sufficient effect of absorbing surge power, that thethickness T3 of the insulating film 2A should be thinner than thethickness T2 of the resistor film 3, and the thickness T4 of the highheat conductor layer 6 should be thicker than T2, preferably twice T2 ormore.

[0032] Although the high heat conductor layer 6 is composed of Al or thealloys thereof, the materials are not limited to these, and the sameeffect can be expected from copper, poly-amorphous silicon, or the like.The same effect can also be expected from a multi-layer wiring structurein which a wiring layer is further provided on the high heat conductorlayer 6 through an insulating film.

[0033] Furthermore, heat capacity can further be increased by making thehigh heat conductor layer 6 wider than the resistor film 3, not only tocover the resistor film 3, as shown in FIG. 2.

[0034] Also, when the high heat conductor layer 6 is used in common withterminal wirings 4A and 4B made of Al or the like, since the area of thehigh heat conductor layer 6 can be increased by using the high heatconductor layer 6 as a part of the ground/power wiring region orinput/output pads, the resistance to surge power of not only anextremely short time such as ESD, but also a relatively long time of themillisecond order, can be improved.

[0035] Since the semiconductor device according to the present inventionis constituted as described above, the resistance to instantaneous surgepower of the semiconductor devices having resistor films can beimproved.

[0036] The entire disclosure of a Japanese Patent Application No.2000-377581, filed on Dec. 12, 2000 including specification, claims,drawings and summary, on which the Convention priority of the presentapplication is based, are incorporated herein by reference in itsentirety.

1. A semiconductor device, comprising: a semiconductor substrate; afirst insulating film formed on said semiconductor substrate; apolysilicon resistor film formed on said first insulating film; a secondinsulating film formed on said resistor film; a high heat conductor filmconsisting of a highly heat-conducting material formed on said secondinsulating film; and a pair of terminal wirings formed on said secondinsulating film and connected to said resistor film, wherein a thicknessof said second insulating film is thinner than a thickness of saidresistor film.
 2. A semiconductor device, comprising: a semiconductorsubstrate; a first insulating film formed on said semiconductorsubstrate; a polysilicon resistor film formed on said first insulatingfilm; a second insulating film formed on said resistor film; a high heatconductor film consisting of a highly heat-conducting material formed onsaid second insulating film; and a pair of terminal wirings formed onsaid second insulating film and connected to said resistor film, whereina thickness of said high heat conductor film is thicker than a thicknessof said resistor film.
 3. The semiconductor device according to claim 2,wherein the thickness of said high heat conductor film is twice thethickness of said resistor film or thicker.
 4. The semiconductor deviceaccording to claim 2, wherein a width of said high heat conductor filmis wider than a width of said resistor film.
 5. The semiconductor deviceaccording to claim 2, wherein said high heat conductor film is unitedwith one of said terminal wirings.